Hope he hand calculated the mileage in OEM form my cluster was constantly 2-3 MPG higher than the actual MPG hand calculated, I corrected it so its closer now.
Since it had larger tires was the ODO corrected? MPG reports need to taken with a little salt. TOO much guess by golly science going around. Put your instant read out mpg on and watch what your foot can do to MPG.
My 2006 Nissan Titan 5.6 2wd UnModified towing the largest Uhaul Trailer they make and loaded for bear got 14 MPG hauling Houston to Phoenix. Lowest spot was 11 coming through the Davis Mountains in West Texas.